Concepts of Theoretical Physics

The concepts of Physics emerge as a sequence and the existence of one gives rise to the presence of the other. Together they form a system of protocol to be followed whenever the subject is learned. This article tries to introduce the concepts of Physics in brief.

The Ten Concepts of Theoretical Physics:

• ·        The physical system and its environment
• ·        Initial state of  the system
• ·        Interaction
• ·        Final state of the system
• ·        Physical quantities
• ·        Laws and principles
• ·        Physical phenomenon or processes
• ·        Theories
• ·        Models
• ·        Vocabulary, conventions and alternative representation

The Physical System and the Environment:

• ·        The object of our study is the Physical system. Everything else surrounding the physical system form its environment.
• ·        For example, a ball is placed on a table. We study the motion of the ball when it is allowed to fall from the table.
• ·        The physical system is the ball. The surroundings comprising of the table and the floor or ground are its environment.

Initial State of the System:

• ·        The physical system in the beginning of the study exists in a particular state. It is called the initial state of the system.
• ·        For instance, the ball is on the top of the table and at a certain height from the floor.

Interaction:

• ·        The physical system and the environment have always influenced each other, as nature is dynamic.
• ·        Though this is a two way process, we can be selective during our study for simplicity.
• ·        We either focus our attention on the influence of physical system on the environment or on the influence of environment on the physical system.
• ·        For example, we study the influence (gravity) of the environment (the floor) on the physical system (the ball).

Final State of the System:

• The state of the physical system post the influence of the environment, is the final state of the system.
• There is a change in the state of the physical system due to its interaction with the environment.
• For example, the ball is finally on the floor.

Physical Quantities:

• ·        There are certain characteristics or properties associated with the physical system and its environment owing to their existence in a particular state.
•      These characteristics or properties are the Physical quantities of the system and its environment respectively.
• ·        There can be several physical quantities of the physical system and the environment owing to their state.
• ·        However, we very selectively focus on only those physical quantities which are of interest with respect to our study.
• ·        For instance, the physical quantities of our interest are the mass of the ball, its final velocity on touching the ground, acceleration due to gravity and the height of the table.
• ·        Physical properties of the system (ball) like its volume, density or the properties of the environment (table) like its width and thickness are immaterial with respect to the outcome of the study and hence ignored.

  

Laws and Principles:

• ·        The change in the state of the physical system causes changes in its physical quantities.
• ·        These changes are described qualitatively and quantitatively by certain physical laws and principles.
• ·        For instance, the falling of the ball from the table on the ground under the influence of gravity is described by the Newton’s Law of Gravitation.
• ·        Certain conservation principles hold good always and further provide insight on the topic, for instance, the conservation principle of energy.

Physical Phenomenon or Processes: 

• ·        Events beginning from the mutual influence of the physical system and the environment, the changes in their states and physical quantities are termed as physical phenomenon or processes.
•      For example, the phenomenon of interest is the motion of a ball from the table on the ground under the influence of gravity.

Theories:

• ·        Scientific theories provide a detailed explanation for the observed physical phenomenon or processes in nature.
• ·        The claims made in scientific theories are based upon  experimental evidences.
• ·        The theories also need to predict the outcomes based on the claims made. They are later verifies by experiments in the laboratory.
• ·        The motion of a ball from the table on the ground under the influence of gravity is explained by the well established theory of gravitation.

Models:

• ·        According to the famous physicist Dr. Neils Bohr, Physics is what we say about nature.
• ·        Nature is very complex to comprehend when considered as it is.
• ·        We study every physical system in nature not as it is, but rather in the form of its model.
• ·        A model is a simplified substitute of the real physical system. It comprises of only those features or properties of the real physical system which are pertinent with respect to the topic of  our interest.
• ·        Models can be classified under four categories. They are simplification model, geometric model, analysis model and structural model.
• ·        This particular concept of physics will be explained in details later.
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• Vocabulary, Conventions and Alternative Representations:
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• ·        As Physics is what we say about nature, our description of nature is in terms of a scientific language framed by us alone.
• ·        It has its own vocabulary, conventions and alternative representations of the findings in the study.
• ·        For example, terms like mass, velocity, acceleration due to gravity, potential energy and kinetic energy are vocabulary.
• ·        The acceleration due to gravity is positive when the object falls towards the ground and is negative when the object moves up, as per the conventions of this subject.
• ·        The motion of the ball from the table under gravity can be represented alternatively in the form of an equation, a table, a picture and a graph.

Conclusion: The cognitive domain of learning Physics comprises of the knowledge of its fundamental concepts. Recall and recognition of these concepts help in the understanding of any topic from any branch of this subject.